Making reflecting lamps



arch 21,

c. BIRDSEYE ET AL ,1L MAKING REFLECTING LAMPS Filed Nov. 9, 1935 Patented Ma -J21, 1939 Clarence Birdseye and Pincus asaignors to Birds Deren, Gloucester, eye Electric Company, Dover, Del., a. corporation of Delaware Application November 9, 1935, Serial No. 49,047

of substantially uniform thickness.

With these problems in mind, the present invention contemplates the employment ofa masking medium capable ofrestricting the silver dethe present invention more readily The masking in de apparent. coating applied to a selected area masking coat itself should not have an appreciable vapor pressure that will permit evena or acidic materials of themselves are not generally useful.

hydrocarbons of high flash point or in a chlorinated solvent which is non-inflammable; but we prefer materials which not only can be applied to'the bulb surface in the molten state mm M avoid the use of any solvent at this point of the operation, but which can be removed from the surface of the bulb following the silvering operation without the use of organic solvents, and by usin a water solution of alkalies and emulsifying agents.

Not 'only are often dangerous and health standpoint, but a considerable period of time is required to remove them from the masking coating before carrying out the silvering operation. Moreover, with materials that cannot be readily removed by alkaline water solutions, and where organic solvents must be employed, it is necessary to rinse out the bulb several times with the fresh solvent in order to remove the last traces of the masking material; and even then it is in most cases necessary water solution of an to be certain that every trace of both solvent masking material is completely removed.

In cases where volatile solvents are used in the application of the masking material, as, for example, a benzol and alcohol solution of gum damar, or an alcohol solution of beeswax, or carbon tetrachloride solution of high melting point paraffin wax, or in all cases where we use alkali or emulsifying agent and a molten material-such, for example, as paraffin containing a small amount of beeswax or rosin, and in general whenever the material itself or the mixture used has an appreciable vapor pressure under the conditions of use, we prefer to remove such vapors continuously as long as the solution remains in the bulb by aspirating air into the bottom of the bulb, and in such a manner that the vapors are diluted and prevented from coming in contact with the walls of the bulb on those areas later to be covered with a silver coating.

In our preferred method for industrial applications of this invention, we use a base material, such as parafiln, erties by adding small amounts of other mate- Paraffin itself has certain of the desired propertiesit is cheap, inert chemically, free from troublesome impurities, is not markedly crystalline and so does not tend to develop cracks between crystals when cooled in thin layers, it melts at a convenient temperature, it can be readily removed with organic solvents and, if care is exercised, it can be removed by hot solutions of alkalies. However, it tends to be greasy and may not always adhere sufiiciently well to the glass to withstand the vigorous agitation of the silvering solution.

We have found that paraffin-preferably of relatively high melting about 135 F.--

" that has been first melted and mixed with from 1% to by weight of dewaxed gum damar will form a satisfactory masking material if applied in the following manner. The bulb surface must be scrupulously clean and ready for silvering, as described in the application above identified, and then the melted mixture is carefully allowed to enter the bulb, which is held rigidly in the desired position. If the temperature of the mix is too low, too thick a coating will result, even if the bulk of the molten mixture is withdrawn immediately. If too hot and immediately withdrawn, the coating will be too thin. Moreover, since the glass bulb is generally cooler than the melted mixture, some of the mixture on entering the cooler bulb tends to solidify at-once, and under these conditions may trap a thin film of expensive and 4 to wash the bulb with a warm.

and adjust certain of its propair between the solidified mixture and the surface of the bulb. Poor adhesion will always occur at these points, unless the temperature of the mix and the time that the full amount of melted mix is allowed to remain in the bulb is suflicient to remelt those parts of the mix which solidified prematurely. That is, if the temperature of the mix is between 160 F. and 190 F. for a 130 F.- melting point parafiin, when it enters the bulb, although some premature solidification will occur, the solidified compound will again melt after perhaps 60 seconds standing. As soon as the mix is uniformly melted the bulk of the material may be withdrawn from the 'bulb. The film left on the masked areaswill rapidly cool and harden and will be of proper thickness and of adequate tackiness to adhere without flecking off during the silvering operation.

We have found that the temperature of application of the mix must be high enough to remelt all of any prematurely solidfied material formed when it first enters the cool bulb, and low enough so that a film of adequate thickness is left on the bulb surface.

The base material of the mix may be any other inert wax, easily removed preferably by hot alkalies, which does not markedly tend to crystallize, such as ceresine or carnauba wax for example.

Instead of the gum damar, of the example above, any other tacky resinous material may be used which will be readily miscible with the hot which will recooling may separate out as a minute dispersion of fine globules in the base material, provided even in this state it remains tacky, such as common rosin or copal or sandarac, for example.

These gums are generally of acidic nature and not only are they of use in the matter of rendering the base material more appear to assist the hot alkaline solution in removing the masking film after the silvering operation. We have been able to remove thin layers of paraflin from bulbs masked in the manner by shaking vigorously for a period with a hot solution, say caustic soda. However, the time required and the amount of shaking is much reduced if the base material contains a few per cent of one of these acidic This is probably because the caustic attacks the acidic comand produces a small amount of a resin soap which aids the hot caustic in forming a crude emulsion of t e softened or even melted mix. Much soap is undesirable since it is difficult to remove the final traces by rinsing with water. This is also true of a caustic solution, and we have after removing by preliminary .continuous rinsings most of the caustic to rinse with a very dilute nitric acid solution-V of 1% for example. Final rinsing of the neutralized surface of the glass with water is rapidly accomplished.

The invention will be more fully understood and appreciated from the following description of several specific examples of ways in which it may be carried out in practice as illustrated in the accompanying drawing, in which- 'Flg. l is a view in elevation of a bulb in position for the application of a masking coat.

Fig. 2 is a similar view of the same bulb inverted and. positioned for the silvering operation.

Fig. 3 is a similar view of the bulb in position for the removal of the masking coating.

Fig. 4 is a view in elevation of a bulb in po- 2,131,049 sition for the application or a masking coat toanother portion of its surface.

Fig. 5 is a view in elevation of a bulb in horizontal position having a masking coat applied to a longitudinal portion thereof.

Fig. 6 is a view similar to- Fig. 2, showing the bulb of Fig. 5 in position {or the siivering oper- -Fig. 1 and masking solution is admitted to the bulb through the tube I? until it rises to the desired level, in the illustrated example, to the line of maximum bulb diameter. The solution in the present instance may be a compound of paraffin with 3% by weight of gum damar and is supplied in melted condition and at a temperature approximating 180 F. This temperature is sufiicient to cause remelting of any of the com= pound which may be chilled and solidified by contact with the cool bulb so as to insure the presence in the bulb of a completely liquid body. As soon as the masking compound has reached the desired level it is at once drawn oil through the tube l2, leaving a thin film ll of the compound firmly adhering to the inner surface of the glass bulb in the selected area.

In order to prevent any vapor of the masking compound from condensing upon the walls of the bulb 10, it is desirable to provide a second tube I3 terminating just short of the desired level of the masking compound, and to suck air concoating. This tends to draw in suflicient air along the walls of the bulb, diluting any vapor Having applied the .inasking coat II to the bulb ID, a predetermined amount of a cool alkaprocedure outlined, in that it is effective to form a uniform silver coating free from pin holes and tightly adherent to the glass of the bulb.

As indicated in Fig. 2 the silver coating H eximportant since the now to be 'removedi'rom er with any silver which may a masking coat. but this is not masking coat is The step of rem plication of the maski e reflecting lamp show n in Fig. 3 is intended particularly for direct lighting, its luminous with a stopper 2 tubes 23, 24, and 25.

which terminates at or r 22. The tube may be modified b plied with-v a brush or is suggested th mg to the portio was left unmasked In Fig. 7. is she e step of applying the n of the bulb which wn a bulb having a masking y step, the coatin covered by the y tipping the d therein; for

' special cases encountered in designing reflecting lamps for a great variety of uses.

Having thus described our invention, what we claim as new and desire to secure by Letters 5 Patent of the United States is:

1. The process of making reflecting electric lamps, which includes the steps of applying to portions of a bulb a masking solution containing components having appreciable vapor pressure under the conditions employed, and withdrawing air from the bulb until the masking medium has solidified therein, thereby preventing condensation on the uncoated inner surface of the bulb.

2. The process of making reflecting electric lamps, which is characterized by the steps of admitting a masking solution to a predetermined level in a bulb, then withdrawing excess solution leaving a film thereof upon the walls of the bulb up to said level, and meantime scavenging the interior of the bulb to remove vapor of the solution therefrom and prevent condensation on the unr coated inner surface of the bulb.

3. The process of making reflecting electric lamps, characterized by the steps of admitting to 9,5 and withdrawing from a bulb a hot liquid masking medium comprising an inert wax containing a small proportion of an acidic resin, thus forming a masking film upon portions of the bulb surface, then admitting a silver-depositing solution to the g0 bulb and finally removing the masking film by a hot alkaline solution.

4. The process of making reflecting electric lamp bulbs, which includes the steps of forcing into the interior of a bulb a predetermined quan- 5 tity of melted wax compound at a temperature substantially above its melting point, and immediately withdrawing the excess while removing vapor from the bulb;

5. The process of making reflecting electric lamp bulbs, which includes the steps of chemically cleaning the inner surface of the bulb, inserting two tubes into the neck of said bulb, forcing through one of said tubes into the interior of said bulb a predetermined quantity of melted 45 wax compound at a temperature substantially above its melting point, and immediately withdrawing the excess by means of the other of said tubes, while removing air and vapor from the interior' of said bulb, silvering the unwaxed inner 50 surface of said bulb while violently agitating the same, and finally removing the wax film by a hot alkaline solution.

6. The process of masking a portion of the inner surface of an electric lamp bulb, which includes the steps of supporting said bulb neck down, closing the neck of the bulb, inserting a first tube in said bulb above a predetermined level, forcing into the interior of'said bulb through a second tube a melted wax compound at a temperature substantially above its melting point and in quantity more than sufiicient to bring the exposed surface thereof above said level, admitting air into said bulb through said first tube while withdrawing air, wax vapor, and excess melted wax by a third tube inserted in the neck of said bulb and reaching to said predetermined level, whereby an exact liquid level is maintained in said bulb, and whereby condensation of wax vapor on the inner walls of said bulb is minimized, and withdrawing the excess of said melted wax compound.

7. The process of producing a reflector upon the inner surface of an electric lamp bulb supported in any position, from its lowest point to any predetermined line, which includes the steps of inserting a tube through the neck of said bulb, placing the open end of said tube adjacent said lowest point of said bulb, forcing a melted wax compound through said tube, into said bulb up to a predetermined level in said bulb, and withdrawing all but a masking film of said melted wax compound through said tube, and then coating the unmasked area of the bulb with arefiecting medium.

8. The process of making reflecting electric lamps characterized by the steps of filling the bowl end of a bulb with a hot masking solution, withdrawing all but a masking film of the solution, filling the bulb from its neck end to approximately its line of maximum diameter, withdrawing all but a masking film of the solution as before, and finally applying a metallic reflecting coating to the bulb area bounded by the separate masked areas thus produced. I

9. The process of making reflecting electric lamps, characterized by the steps of successively filling different portions of the bulb with a masking solution to cover separate areas spaced from each other upon the inner surface of 'the bulb and successively withdrawing all but a masking film of the solution, meanwhile scavenging the interior of the bulb to prevent condensation on its uncoated area, and then applying a reflecting coating to the area set of! by said masked areas.

CLARENCE BIRDSEYE. PDICUS DEREN. 

